The transcriptional coactivator PGC-1alpha plays a central role in lipid metabolism; although its specific regulatory functions have been extensively studied, not much is known about the identity of potential interacting molecules that could act as coregulators and switch on or off its activity in response to metabolic cues. We have undertaken a biochemical approach followed by mass spectrometry and recently characterized a novel PGC-1alpha binding molecule that is able to enhance PGC-1alpha's transcriptional activity in vitro. By gain-and loss-of-function experiments, we are currently assessing the effects of this novel cofactor on the expression of genes regulated by PGC-1alpha and we are determining its overall effects on lipid beta-oxidation in vivo.